1. Field of the Invention
This invention relates to methods and kits for detecting the presence of chemical warfare agents and degradation products thereof. More particularly, the invention relates to an accurate and rapid method of detecting the presence of chemical warfare agents, precursors of chemical warfare agents, and degradation products of chemical warfare agents in a sample.
2. Description of the Prior Art
Over the years, various highly toxic chemical warfare agents (CWA""s) have been developed and stockpiled by several nations. In view of the health hazards associated with CWA""s and degradation products thereof, a Chemical Weapons Convention (CWC) has been developed by certain countries. The CWC monitors, detects and identifies and, if necessary, disposes of CWA""s which are not in compliance with the convention. As a result of the convention, it is often necessary to conduct inspections of various sites in order to assure compliance.
On-site analysis of sample unknowns in CWC verification inspections is preferred to off-site analysis. Some reasons for this preference include:
a) existing agreements call for on-site analysis;
b) when samples are analyzed on-site, ambiguities can be resolved during the inspection;
c) since unknown samples are not removed from the inspection site, contamination and cross-contamination of samples during travel to off-site laboratories cannot occur; and
d) since ambiguities will be resolved on-site during the inspection, the inspection report that is completed at the end of the inspection would not be subject to challenge.
One of the requirements for the screening methods employed in on-site inspections is that they be essentially non-intrusive. Every possible effort must be made to utilize analytical methods that do not disclose sensitive corporate or governmental information during on-site inspections. Reagent-based screening methods are attractive because many tests can be run in a short period of time and, since they give only a positive or negative response, they are capable of providing presumptive evidence for a prohibited substance in a sample without revealing the identity of any of the components in the sample.
Consequently, a number of reagent based screening tests have been included in the initial operating capability (IOC) for the on-site CWC verification inspections. Unfortunately, these tests do not have a high degree of detection specificity.
Classical spot tests are usually carried out in a porcelain spot plate containing depressions to which detector reagents are added. In practice, a small amount of a test sample, hereinafter, xe2x80x9ca sample unknownxe2x80x9d is placed in one or more of the depressions of the spot plate. Small quantities of one or more reagents are then added to it. A positive test is usually signified by a color change. As many as 12 different spot tests can be carried out in a small (3.5 inchxc3x974.5 inch) spot plate. In most cases, the lower limit of detection is in the 1-100 microgram range.
In view of the advantages of rapidly and accurately identifying the presence of CWA""s and associated by-products, there is a need for rapidly and accurately detecting submicrogram quantities of CWA, CWA precursors and related degradation byproducts.
The invention provides a method of detecting the presence of chemical warfare agents, chemical warfare agent precursors and degradation products thereof, (hereinafter xe2x80x9canalytesxe2x80x9d). This method includes the steps of contacting a sample suspected of containing a member of the group consisting of chemical warfare agents, chemical warfare agent precursors, chemical warfare agent degradation products and mixtures thereof with a sufficient amount of a chromatographic adsorbent material and a sufficient amount of a chromogenic detector reagent, so that a chromogenic indicator is formed when the sample contains a member of the aforementioned group of chemical warfare agents. A particular application is a method for detecting the presence of an alkyloxy methylphosphonic acid, comprising the steps of reacting the alkyloxy methylphosphonic acid with a dehydrating agent so that a cholinesterase inhibitor is produced and then detecting the presence of the cholinesterase inhibitor. Another application is a method for detecting the presence of methylphosphonic acid, comprising the steps of reacting the methylphosphonic acid with an esterification agent so that an alkyloxy methylphosphonic acid is formed, then reacting the resultant alkyloxy methylphosphonic acid with a dehydrating agent so that a cholinesterase inhibitor is formed, and then detecting the presence of the cholinesterase inhibitor. A further application is a method for detecting the presence of methylphosphonofluoridic acid, comprising the steps of reacting the methylphosphonofluoridic acid with a suitable esterification agent so that an alkyloxy methylphosphonofluoridate, a cholinesterase inhibitor, is formed, and then detecting the presence of the cholinesterase inhibitor.
Another aspect of the invention provides a kit for chromogenically detecting the presence of chemical warfare agents, chemical warfare agent precursors and degradation products thereof. The kit includes a means for obtaining a sample suspected of containing a member of the group consisting of chemical warfare agents, chemical warfare agent degradation products and mixtures thereof, chromatographic sorbent material, chromogenic detector reagents, and a means for reacting the sample on a chromatographic sorbent material with a chromogenic detector reagent so that a chromogenic indicator can be formed when the sample contains one of the aforementioned members of the group.